Disk device

ABSTRACT

According to one embodiment, a disk device includes a disk-shaped recording medium, a base accommodating the recording medium, the base including a bottom wall, a sidewall on a peripheral portion of the bottom wall, and a rib on a part of an upper surface of the sidewall, a first cover on a part of the upper surface of the sidewall, and a second cover on a first surface of the rib and above the first cover. The rib includes a first region with a first width, a second region with a second width less than the first width, and the first surface with a fixed width around an entire circumference of the rib. The first region and the second region are located corresponding to a side portion of the recording medium.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 16/855,286filed Apr. 22, 2020 which is a continuation of application Ser. No.16/284,308 filed Feb. 25, 2019 and is based upon and claims the benefitof priority from Japanese Patent Application No. 2018-168876, filed Sep.10, 2018, the entire contents of which are incorporated herein byreference.

FIELD

Embodiments described herein relate generally to a disk device.

BACKGROUND

As a disk device, a magnetic disk drive comprises a housing including abase and a top cover, and the housing accommodates therein a rotatablemagnetic disk, an actuator supporting a magnetic head and the like. As atechnique of improving the performance of the disk drive, a method ofreducing rotational resistances of the magnetic disk and the magnetichead, by sealing low-density gas in the housing, has been proposed.

In such a magnetic disk drive, the top cover is jointed to the base ofthe housing by welding to form an enclosed housing and increase theairtightness of the housing. The welding is carried out on along anentire outer circumference of the top cover. Here, in order to obtainhigh airtightness, it is necessary to maintain a stable welding qualityall around the circumference. On the other hand, in the case where theouter diameter of the magnetic disk, the wall portion of the base needsto be formed thinner, which may accordingly decrease the area of thewelded portion and degrade the welding quality.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a hard disk drive (HDD) accordingto a first embodiment.

FIG. 2 is an exploded perspective view of the HDD while an outer coverthereof being removed.

FIG. 3 is an exploded perspective view of the HDD while an inner coverthereof being removed.

FIG. 4 is a perspective view showing an inner side of the inner cover.

FIG. 5 is an exploded and enlarged perspective view of a recess portionof a base and a protruding portion of the inner cover.

FIG. 6 is a cross sectional view of the HDD taken along line A-A of FIG.1.

FIG. 7 is a cross sectional view of the HDD taken along line B-B of FIG.1.

FIG. 8 is an enlarged perspective view showing a side wall portion of anHDD according to a second embodiment.

FIG. 9 is a cross-sectional view schematically showing a side wallportion, to illustrate a step of processing the side wall portion.

DETAILED DESCRIPTION

Various embodiments will be described hereinafter with reference to theaccompanying drawings. In general, according to one embodiment, a diskdevice comprises a disk-shaped recording medium; a base accommodatingthe recording medium, the base comprising a bottom wall, a sidewall on aperipheral portion of the bottom wall, and a rib on a part of an uppersurface of the sidewall, the rib comprising a first region with a firstwidth, a second region with a second width less than the first width,and a first surface with a fixed width around an entire circumference ofthe rib, the first region and the second region being locatedcorresponding to a side portion of the recording medium; a first coverprovided on a part of the upper surface of the sidewall; and a secondcover provided on the first surface of the rib and provided above thefirst cover.

First Embodiment

As a disk device, a hard disk drive (HDD) according to the firstembodiment will be described in detail. FIG. 1 is a perspective viewshowing the appearance of the HDD according to the embodiment, and FIGS.2 and 3 are exploded perspective views of the HDD when decomposed.

As shown in FIGS. 1 to 3, the HDD comprises a flat and substantiallyrectangular housing 10. The housing 10 comprises a base 12 in the shapeof a rectangular box whose upper surface is open, an inner cover (firstcover) 14 which is secured to the base 12 by a plurality of screws 15and closes an upper end opening of the base 12, and an outer cover(second cover) 16 which is located above the inner cover 14, and whoseperipheral edge portion is welded to the base 12. The base 12 comprisesa rectangular bottom wall 12 a opposing the inner cover 14 with a gaptherebetween, and sidewalls 12 b standing along edges of the bottom wall12 a, which are formed integrally as one body from an aluminum alloy.The sidewalls 12 b include a pair of long sidewalls 13 a opposing eachother and a pair of short sidewalls 13 b opposing each other. An innersurface of one of the short sidewalls 13 b and an inner side surface ofabout ⅔ region of each long sidewall 13 a are formed into an arcuateshape curved along an outer circumferential edge of a magnetic disk 18,which will be described later. A substantially rectangular frame-shapedfixing rib 12 c is provided on an upper end surface 38 of each sidewall12 b. The fixing rib 12 c is formed integrally with the respectivesidewall 12 b as one body, thus constituting a part of the sidewall 12b. The fixing rib 12 c will be described in detail later. The region ofthe upper end surface 38 which is located inside the fixing rib 12 cconstitutes a mounting surface (38) on which the inner cover isarranged.

The inner cover 14 is formed into a rectangular plate-shape fromstainless steel, for example. The inner cover 14 has a shape anddimensions corresponding to those of the fixing rib 12 c of the base 12.That is, the inner cover 14 has an outer circumferential shapecorresponding to the inner circumferential shape of the fixing rib 12 cand is formed to have outer dimensions slightly less than innerdimensions of the fixing rib 12 c. As shown in FIG. 4, a rectangularframe-shaped gasket 17 or a sealing material is provided on an innersurface of the inner cover 14. The gasket 17 extends near and all alongthe outer circumferential edge of the inner cover 14. The gasket 17 isformed by applying a sealing material, for example, UV-curing resin orthe like by a predetermined width on the inner surface of the innercover 14, followed by curing.

As shown in FIGS. 2 and 3, the inner cover 14 is disposed on the upperend surface (the mounting surface) 38 of the sidewalls 12 b and on aninner side of the fixing rib 12 c. The circumferential portion of theinner cover 14 is placed on the mounting surface 38 of the sidewalls 12b via the gasket 17. A plurality of locations of the circumferentialportion of the inner cover 14, that is, for example, four cornerportions and a longitudinal central portion, are screwed to the upperend surfaces 38 of the sidewalls 12 b with screws 15. Thus, the innercover 14 airtightly closes the upper opening of the base 12. The sideedges (side surfaces) of the inner cover 14 oppose the inner sidesurface (second surface) of the fixing rib 12 c with a slight gaptherebetween.

The fixing rib 12 c is formed to have a height greater than thethickness of the inner cover 14. As shown in FIG. 2, in the state wherethe inner cover 14 is attached to the base 12, the fixing rib 12 cprotrude up over the inner cover 14.

As shown in FIGS. 1 and 2, the outer cover 16 is formed into arectangular plate shape from aluminum alloy, for example. The outercover 16 has an outer circumferential shape and dimensions substantiallyequal to the outer circumferential shape and outer dimensions of thefixing rib 12 c. That is, the outer cover 16 is formed to be slightlygreater in dimensions than the inner cover 14. The outer cover 16 isdisposed on the fixing rib 12 c, to cover the inner cover 14. Theperipheral portion of the outer cover 16 is welded to the fixing rib 12c all around thereof and fixed airtightly to the base 12.

In the inner cover 14 and the outer cover 16, vent holes 46 and 48through which the interior of the housing 10 and the exterior of thehousing 10 are communicated with each other are formed, respectively.The air in the housing 10 is exhausted through the vent holes 46 and 48,and further, through these vent holes 46 and 48, a low-density gas(inert gas) having a density lower than that of air, for example, ahelium, is enclosed in the housing 10. Then, a sealant (a sealing body)50 is attached to the outer surface of the outer cover 16 so as to closethe vent hole 48.

As shown in FIG. 3, in the housing 10, a plurality of magnetic disks 18as recording media, and a spindle motor 20 as a drive unit whichsupports and rotates the magnetic disks 18 are provided. The spindlemotor 20 is disposed on the bottom wall 12 a. Each magnetic disk 18 isformed so as to have a diameter of, for example, 95 mm and comprises amagnetic recording layer on the upper surface and/or lower surface. Themagnetic disks 18 are engaged coaxially with a hub (not shown) of thespindle motor 20, clamped by a clamp spring 27, and thereby fixed to thehub. In this manner, the magnetic disks 18 are supported in parallel tothe bottom wall 12 a of the base 12. The magnetic disks 18 are rotatedat a predetermined number of revolutions by the spindle motor 20.

In this embodiment, five magnetic disks 18, for example, areaccommodated in the housing 10. But, the number of magnetic disks 18 isnot limited to five, and can be increased or decreased. Further, asingle magnetic disk 18 may be accommodated in the housing 10.

In the housing 10, a plurality of magnetic heads 31, which record andreproduce information on and from the magnetic disks 18, and a headactuator assembly 22, which supports the magnetic heads 31 such thatthey are movable with respect to the magnetic disks 18, are provided.Further, the housing 10 accommodates a voice coil motor (hereinafterreferred to as VCM) 24 which rotates and positions the head actuatorassembly 22, a ramped loading mechanism 25 which holds the magneticheads 31 at an unloading position away from the magnetic disks 18 whenthe magnetic heads 31 are moved to the outermost circumference of themagnetic disks 18, and a board unit 21 on which electronic componentsincluding a conversion connector are mounted.

The head actuator assembly 22 includes an actuator block 22 in which abearing unit 28 is built, a plurality of arms 30 extending from theactuator block, and a suspension 34 extending from each of the arms 30,and the magnetic head 31 is supported by the distal end portion of eachof the suspensions 34. The head actuator assembly 22 is supportedpivotably by a pivot disposed to stand on the bottom wall 12 a via thebearing unit 28.

Onto the outer surface of the bottom wall 12 a, a printed circuit board(not shown) is fixed by screws. A control unit is formed on the printedcircuit board and the control unit controls the operation of the spindlemotor 20, and also controls the operation of the VCM 24 and the magneticheads 31 via the board unit 21.

Next, the structure of the fixing rib 12 c and the structure of a weldedportion will be described in detail.

FIG. 5 is an exploded and enlarged perspective view of a recess portionof the base and a protruding portion of the inner cover. FIG. 6 is across sectional view of the HDD taken along line A-A of FIG. 1. FIG. 7is a cross sectional view of the HDD taken along line B-B of FIG. 1.

As shown in FIGS. 3 and 5 to 7, the rectangular frame-shaped fixing rib12 c provided integrally on the upper end surfaces 38 of the sidewalls12 b comprises a flat ceiling surface (welding surface) (first surface)SW having a fixed height T1 all along the entire circumference. Thefixing rib 12 c is, in its most part, formed as a first area (broadportion) 30 a having a first width W1 which is fixed. At least a portionof the fixing rib 12 c, in this embodiment, three locations thereofconstitute a narrow region (second region) 30 b having a second widthW2, which is less than the first width W1. The three narrow regions 30 bare provided in three locations, which includes two locations on theright and left side of the long sidewall 13 a located most adjacent tothe outer circumferential edge of the magnetic disk 18 and the centralportion of one short sidewall 13 b. The narrow regions 30 b are eachformed by, for example, cutting the inner surface (second surface) ofthe fixing rib 21 c, which is on the side of the magnetic disk 18, intoa long and slender rectangular recess portion 32, to narrow down thewidth of the fixing rib 12 c. The recess portions 32 are each recessedin a direction away from the magnetic disk 18, to have a depth of, forexample, about 0.1 to 0.3 mm. With the recess portions 32 thus provided,a bottom surface of each recess portion 32 serves as an installationsurface flush with the mounting surface 38, and thus it becomes possibleto keep wide the width of the mounting surface 38 abutted to the gasket17 of the inner cover 14. The longitudinal length L1 of each narrowregion 30 b is, for example, about 20 to 40 mm. The length L1 isarbitrarily settable and can be changed if needed.

The inner circumferential corner portions of the fixing rib 21 c, i.e.,the corner portions where the ceiling surface and the inner surfaceintersect each other, are each cut off at a predetermined angle, to forma C surface (chamfered surface) (third surface) CH having apredetermined width. The C surface CH is formed all around thecircumference of the fixing rib 21 c in both of the first region 30 aand the second region 30 b. In this case, a width CW2 of the C surfaceCH in the second region 30 b is less than a width CW1 of the C surfaceCH in the first region 30 a. Thus, the flat ceiling surface (weldingsurface) (first side) SW which remains in the fixing rib 21 c is formedto have a fixed width W3 all around the entire circumference. That is,in any region of the first region 30 a and the narrow regions 30 b, awelding surface SW having the width W3 is maintained.

The peripheral portion of the outer cover 16 is placed on the weldingsurface SW of the fixing rib 21 c and welded to the welding surface SWby, for example, laser welding. The welding surface SW is formed to havea fixed width W3 all around the entire circumference of the fixing rib21 c and the welding surface SW of the constant width W3 is maintainedin each narrow region 30 b as well. With this structure, the peripheralportion of the outer cover 16 can be welded to the fixing rib 12 c in astable manner, and the first region 30 a and the second region 30 b canmaintain high welding quality. Although the width W3 of the weldingsurface SW may slightly vary upon welding the outer cover 16 to thewelding surface SW, the welding surface SW maintains a substantiallyfixed width W3 all around the entire circumference of the fixing ribafter welding.

On the other hand, as shown in FIGS. 2 and 5 to 7, the inner cover 14comprises three projecting portions 40 integrated to the cover 14, whichrespectively correspond to the recess portions 32 of the fixing rib 21c. In other words, the projecting portions 40 are formed respectively inthe long sides and a central portion of a short side of the inner cover14. The length and the height of each projecting portion 40 are setslightly less than the length and recession of the recess portions(narrow regions) 32. The projection height is, for example, about 0.1 to0.2 mm.

As shown in FIG. 4, the gasket 17 provided on the inner surface of theinner cover 14 is turned outwards in the locations of the projectingportions, and extends along the end edges of the projecting portions.While the inner cover 14 is fixed by screwed to the upper end surfaces(mounting surfaces) 38 of the sidewalls 12 b, the projecting portions 40are located in the respective recess portions 32 of the correspondingnarrow regions 30 b, and further tightly attached onto the mountingsurface 38 via the gasket 17.

According to the HDD configured as described above, even in the casewhere the diameter of the magnetic disk 18 is increased and thethickness of the sidewalls 12 b of the base 12 is decreased, recessportions 32 are made in locations of the fixing rib 21 c, whichcorrespond to the thin portions, to form the narrow regions 30 b, andfurther the chamfer width of the narrow regions 30 b is set less thanthe chamfer width of the first regions 30 a. In this manner, asufficient width of the welding surface can be maintained for the fixingrib. Thus, the peripheral portion of the outer cover 16 can be welded tothe sidewalls 12 b of the base 12 while maintaining high welding qualityall around the entire circumference. Therefore, the magnetic disk can beincreased in diameter and the storage capacity can be increase whilemaintaining the welding quality. Moreover, with the recess portions 32thus provided, the width of the mounting surfaces can be expandable bythe depth of the recess portions 32. With this structure, even in theregions where the sidewalls 12 b are thin, the gasket 17 of the innercover 14 is reliably brought into contact with the mounting surfaces ofthe sidewalls, thereby making it possible to keep high airtightness. Atthe same time, the gasket 17 can be disposed to be apart from the outercircumferential edge of the magnetic disk 18 by only a predetermineddistance.

In the embodiment described above, the C surface is formed all aroundthe entire circumference of the fixing rib 21 c, burrs and the like,which may be produced at the time of manufacture can be removed, andtherefore the flatness of the welding surface SW can be secured.Therefore, it is possible to suppress the degrading of the flatness ofthe welding surface or deterioration in welding quality, caused byburrs.

Next, an HDD according to another embodiment will be described. In theembodiment to be described below, the same structural members will bedenoted by the same reference numbers as those of the first embodimentprovided above, and the detailed explanations thereof will be omitted.Only the parts different from those of the first embodiment will bemainly described in detail.

Second Embodiment

FIG. 8 is a partially enlarged perspective view showing a base of an HDDaccording to the second embodiment and FIG. 9 is a cross-sectional viewschematically showing the base to illustrate a step of processingsidewalls of the base.

As shown in FIG. 8, only the first region 30 a of the fixing rib 21 cprovided on a sidewall 12 b may be chamfered to form a C surface (thirdsurface) CH without chamfering the narrow region 30 b. In other words,such a structure that the narrow region 30 b does not comprise a Csurface may be accepted. When not chamfering, there may be a case whereburrs remain in a corner portion of the narrow region 30 b. To avoidthis, when processing the fixing rib 12 c of the base 12, it ispreferable to, first, cut the surface where burrs are created in thenarrow region 30 b to remove the burrs, and thereafter cut the othersurfaces as shown in FIG. 9. For example, when burrs are created on thewelding surface SW of the narrow region 30 b, it is preferable to cutthe welding surface CW first, and then cut the inner side surface of thefixing rib 21 c, that is, the bottom surface of the recess portion 32.On the other hand, when burrs are created on the inner surface of thefixing rib 21 c, it suffices if the inner side surface is cut first, andthen the welding surface CW is cut.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

The locations where the narrow regions are formed in the fixing rib ofthe housing are not limited to those of the embodiments provided above,but these regions may be provided in any locations. Further, the narrowregions of the fixing rib are not limited to three, but there may beone, or two or four or more regions. The materials, shapes and sizes ofelements constituting the disk drive can be changed as needed. In themagnetic disk device, the number of magnetic disks and magnetic headscan be changed as needed. The size of the magnetic disks can be selectedin various ways.

What is claimed is:
 1. A disk device comprising: a recording medium; abase accommodating the recording medium, the base comprising a bottomwall, a sidewall on a peripheral portion of the bottom wall, and a ribon a part of an upper surface of the sidewall, the rib comprising afirst region with a first chamfered surface with a first chamfered widthand a second region with a second chamfered surface with a secondchamfered width which is less than the first chamfered width, the firstregion and the second region being located corresponding to a sideportion of the recording medium; a first cover provided on a part of theupper surface of the sidewall; and a second cover provided on the riband provided above the first cover.
 2. The disk device of claim 1,wherein the rib comprises a first surface with a fixed width around anentire circumference of the rib, and a second surface provided on aninner side portion of the rib, and the first chamfered surface and thesecond chamfered surface are provided between the first surface and thesecond surface.
 3. The disk device of claim 2, wherein the rib comprisesa third surface provided only between the first surface and the secondsurface in the first region of the rib.
 4. The disk device of claim 3,wherein the third surface has a width in the second region, which isless than a width of the third surface in the first region.
 5. The diskdevice of claim 1, wherein the rib comprises a recess portion in whichthe second region comprises a bottom portion, and the first covercomprises, in an outer peripheral portion thereof, a projecting portioncorresponding to the recess portion of the rib.
 6. The disk device ofclaim 1, wherein the sidewall of the base comprises a pair of longsidewalls, and a pair of short sidewalls, and the second region of therib is provided on each of the long sidewalls and one of the shortsidewalls.
 7. The disk device of claim 1, wherein a gas of a densitylower than that of air is sealed with the base and the first cover. 8.The disk device of claim 2, wherein the sidewall of the base comprises apair of long sidewalls, and a pair of short sidewalls, and the secondregion of the rib is provided on each of the long sidewalls and one ofthe short sidewalls.
 9. The disk device of claim 2, wherein a gas of adensity lower than that of air is sealed with the base and the firstcover.
 10. The disk device of claim 1, wherein the second region is morecloser to the side portion of the recording medium than the firstregion.
 11. The disk device of claim 1, wherein the rib is formedintegrally with the sidewall.